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Technique and Training

How to Master the Bottom Half of Butterfly

Building the back half of your butterfly takes a lot of work

Terry Heggy | February 8, 2018

Butterfly with a great kick evokes the image of a powerful aquatic beast lunging through the surf, powering forward with undulating grace and awe-inspiring beauty. Yet many of us swim butterfly looking less like Flipper and more like hobbled jellyfish.

But considerable improvement is possible with a simple commitment to practice while concentrating on form. Here are four focal points for a better butterfly kick.


Effective butterfly involves moving forward in a motion approximating a sine wave. There’s a crest (high point) and a trough (low point) that each body part passes through during the stroke cycle. You may think you’ve mastered the wave motion because your head is moving up and down, but you can be bobbin’ your noggin like crazy while your legs are dragging on the bottom of the pool. It’s the motion of the hips that tell the truth about your butterfly kick success.

Pay attention to your hips as you swim butterfly and feel them follow the wave. If they remain low throughout the stroke, your body develops a vertical orientation that creates tremendous resistance. When your hips rise as you reach for the catch, it minimizes your overall drag profile.

Remember that the wave is moving forward like a dolphin, not merely up and down like an inchworm. If you are unable to get your hips to come up to the crest of the waveform, check to make sure your head is getting down and that you are extending your arms fully for the catch. If that doesn’t solve the problem, then it’s likely a conditioning issue. Improve your leg power by doing more dolphin kick in practice and increase your dryland work for the muscles of your core.


Most people are pretty good at using their quadriceps (thigh muscles) on butterfly kick but neglect the hamstrings (the muscles on the back of the upper leg). In other words, they’re good at kicking down, but forget that the upward component is also supposed to be propulsive, not merely a floating recovery. Kick in both directions, but don’t over-bend the legs; the angle at the knee should always be more than 90 degrees.

To improve awareness of the hamstring-driven part of the kick, practice doing dolphin kick vertically in deep water. Notice how your kick becomes more powerful when you get your abdominal muscles involved.


If your toes point toward the bottom of the pool, your feet act as drag chutes, catching water and slowing you down. Work on ankle flexibility with dryland stretching so your feet will always be oriented for propulsion rather than drag.

Also monitor the depth of your feet. Your feet shouldn’t get much below the drag profile created by your torso (usually about 18 inches or so beneath the surface). They should also come back up in the same general sine wave pattern that your hips follow, but make sure your feet don’t lose contact with the water. If your feet are entirely visible above the surface, they’ll create power-robbing turbulence as they smack the water. If you hear that big ker-thump sound when you kick, shrink the motion of your kick to keep it in the water and in line with your body.


Eliminate dead spots in your dolphin kick by taking the steps mentioned above (especially the “do more dolphin kick in practice” and “more core work on dry land” parts). Keep a high tempo during kick sets, even when you use fins. If that doesn’t get your kick to flow in a quick, continuous power cadence, then examine the front half of your stroke. Common problems include the following:

  • Failure to exhale. If you don’t start expelling air early enough in your stroke, you’ll build up CO2, which makes you think you can’t breathe.
  • Too much glide (aka pausing for no reason) during the catch phase.
  • Head too high. If you don’t get your eyes back down after the breath, your body loses the rhythm of the wave.

We’ll address front-half solutions in another article. But keep in mind that the elements we’ve discussed all work together, so being able to maintain a good cadence provides the verification that the hips, hamstrings, and feet are all working properly.

To master each of these pieces, do a set of five broken 100s of full-stroke butterfly, with a focus on hips on the first length, hammies on the second, feet on the third, and cadence on the fourth. Take adequate rest between lengths so that you’re able to maintain a quality kick on each length. As you get stronger, shorten that rest. Mastering butterfly takes a lot of work, so be patient and stick with it; feeling like Flipper is worth the extra effort!

USMS Wave Seperator

About the Author—Terry Heggy

Terry "Speed" Heggy has been swimming for more than 50 years. He won his age group in the 10K Open Water Championship in 2006, competed in the National Championship Olympic Distance Triathlon in 2014, and qualified again for USAT Nationals in 2015. He's the head coach of Team Sopris Masters in Glenwood Springs, Colo., and is a USMS-certified Level 3 Masters coach and an NASM Certified Personal Trainer.

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